The invention relates to an arrangement for apportioning the idling air of an internal-combustion engine which includes a motor driven air flow adjusting member and a supplementary device for controlling the adjusting member into a minimum opening position when the engine is rendered inoperative.
In the case of internal-combustion engines equipped with "motronics", devices of this type are provided with an electric adjusting motor. Furthermore, in a known construction, this electric adjusting motor acts upon the adjusting member only in the opening direction, whereas, in the closing direction, the adjusting member is acted upon by a spring. Concerning this state of the art, it is stated in German Published Unexamined Patent Application (DE-OS) 32 34 468 that, when the power supply to the electric adjusting motor is interrupted, the adjusting member can be moved into a position by the spring element which ensures a minimum opening of the flow control cross-section. This results in an idling arrangement with an emergency cross-section.
The disadvantage of this known idling arrangement is the fact that an electric winding power (change of resistance) which is a function of the outside temperature must work against a constant spring force. This results in undesirable nonlinearities of the characteristic control line.
The object of the above-mentioned DE-OS 32 34 468 is an idling arrangement with an electric adjusting motor which has a driving effect in the opening and in the closing direction. In this known arrangement, a separate opening for the formation of an emergency cross-section is assigned adjacently to the flow control cross-section to be controlled by the adjusting member. However, in this case, the adjusting member is constructed such that, in a certain position, it covers the flow control cross-section as well as the emergency cross-section and, in this position, the emergency cross-section is made inoperative by means of a mechanical blocking of the adjusting member. The air, which flows in solely by way of leakages of the internal-combustion engine, is not sufficient for a reliable starting.
In both above-mentioned cases, a supplementary device, which can be activated when the internal-combustion engine in rendered inoperative, is used for controlling an emergency cross-section open by means of the adjusting member.
It is an object of the invention to develop an arrangement of the above-mentioned type such that a predetermined emergency cross-section is ensured while the above-mentioned disadvantages are avoided.
This object is achieved according to preferred embodiments of the invention by providing an arrangement wherein the supplementary device comprises two magnets arranged to mutually affect one another, one of the magnets being configured to be rendered essentially inoperative when the internal-combustion engine is operating. By means of the invention, a minimum opening of the flow control cross-section serving as an emergency cross-section is achieved by two magnets arranged to affect one another, in which case one of the magnets arranged at the adjusting member or at a housing for the adjusting member achieves its full effect only when the internal-combustion engine is rendered inoperative. Thus, in every case, when the internal-combustion engine is started, an emergency cross-section is advantageously ensured. During the subsequent operation of the internal-combustion engine and when the idling arrangement is operating, one of the magnets is essentially rendered inoperative so that a control or a linear characteristic curve of the idling arrangement is advantageously not disturbed.
A supplementary device which has a simple construction according to preferred embodiments of the invention utilizes the arrangement of two permanent magnets, in which case one of the permanent magnets is correspondingly combined with an electric coil, for the purpose of a significant weakening of its magnetic field while the idling arrangement is operative. The significant advantage of this supplementary device is the fact that it becomes operative automatically as soon as the internal-combustion engine becomes inoperative for any reason; for example, if the internal-combustion engines dies after a cold start.
Another advantageous development of preferred embodiments provides a supplementary driving device of the adjusting member without any external energy by configuring the uncontrollable permanent magnet with a linear extension which is directed in the same direction as the moving direction of the adjusting member with magnetic fluxes which differ in the opposing end areas, the end area with the lowest magnetic flux, in the case of the largest opening of the flow control cross-section, being adjacent to the area of the effect of the controllable permanent magnet. This results in the additional advantage that, when the idling arrangement is operating defectively, no flow control cross-section is adjusted or controlled that is larger than the predetermined emergency cross-section. A simple design of the uncontrollable permanent magnet for an adjusting member constructed as a rotary slide for this purpose utilizes a crescent shaped permanent magnet.
In certain other contemplated preferred embodiments, the adjusting member is configured as a reciprocating lifting piston.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.